Water treatment



H. V. SMITH ETAL,

I July 31, 1945.

WATER TREATMENT Filed May 20, 1939 INVENTOR. HOWARD V. SMITH, BY SM TH.

7 ATTORNEY.

w factory in one. way

practical standpoint.-

Poteiilz'ed 4 My ,wl ee' sanm': I 'fnomytsjmus mounts- Smiths a v I lzois'lme. This inventlonreiat'es to the treatment or water and, morefparticulaflm to the purification of potable waters for the. removalor correction-oi certain undesirable orharmful/characteristics of such waters, or .of other liquids designed for hue man consumption. 1

.' Specifically, the invention contemplates a treatment for potable waters or other liquids which are contaminated, either through natural'o'ccurrence or through incidental inclusion, withl fluorine,

fluorides or other fluorine compounds in-such amounts that habitual consumption of the liquids is harmful or dangerous for the human system.

and particularl'yior the teeth. The-primary aim of the invention is to remove the fluorine or fluorides from: such liquids or at least; to reduce. the fluorine content to an amount below that order that it may be used repeatedly in. fluorine Y which has been-determined toexert tonic effects upon the human system.

J Since about .1931, when theone or mottled enamel, an irreparable defect of human tooth" was found by the applicants herein to be due to excessive amounts of fluorine in drinking water. there has been sought a method or its. removal from water supplies which would be eflective andeiiicient but at the 'sametime economically attractive; The problem has been a diflicult one, because of the small amounts of fluorine present in drinking water. The continuoususeoi water containing as .little as .9 partper million of fluorine has been foundt'ocause mottled enamel.v

Certain methods 01' fluorine removal have been proposed heretofore but have. either proved ,in-

--'ground bone results in'the'reduction oi the fluoeflective for thelowering of the fluorine concen- 'tration in watersufliciently to prevent mottling of teeth. or have proved impracticalin their actual operations, generally vfrom aneconomic stand:

point. The use-of aluminum sulfatetor fluorine removal has been suggested, butthis method is at the most quite costly and sometimes unreliable 'Another proposal has been the use of activated: carbon but disadvantages inherent inthat method not take'place above apH of-3.; [Other proposals 7 are the high seen of activated carbon ,andthey, fact that satisfactory absorption of fluorine would have used activated alumina andthe lime-soda method familiar. in water. softening." .All;o1:.these'-'v I previous methods have proved generally unsatisoranother, at least from a It isan object 01' the present invention-to providea method forthe removal of fluorine from -iiuorine containing waters or other potable 1 liquids, or for thelowering of the fluorine con- 'centration; therein ll point below that which in which? e uals 2 or 3. f It has been found that vis toxic to simple, highly effective and economically attrective. v

. Another object is to provide a specially prepared material which will remove or reduce the fluorine in water, possibly by an exchange reaction.

Another obiect'is to'providea manner of treat- I 'ing such material for vthe purpose of rendering itmost eilicient in flu'orineremoval action.

A further object is to provide a simple and effective method of regenerating the material in removal treatment. V

A'still i'urther object is to provide a relatively simple apparatus; in the form of a water-cooling and dispensing device which may be readily sedin' homes, oflices, schools and the like; which will effectively lower the fluorine content in the water below that point which is acknowledged to be toxic;

The method oi the present: invention depends I upon'the afllnity of bone, or other naturalor ar-' 'tiflcially preparedapatlte ior fluorine. Chemical analysis and microscopic and X-ray retraction ex= amlnations indicate that bone is a carbonate apatite with the probable formula oi ncauroo 2.0:;003

treatmentoi fluorine-bearing water with finely vrine concentration so as to render the water potable and harmless tocause-the serious enamel mottling. Since the fluorine is present in natural waters in the form of. fluorides, probably mainly o'i'calcium and sodium,- it is logical to believe that fluorine may replace the carbonate radical in the above exemplified carbonate apatite ,-with the formation o'i an insoluble final-apatite,

leaving the harmless calcium and sodium -carbonate in the water "in; place of thedangerou's fluorides. By the'sax'ne'ltoken other apatite com pounds would have a similar afllnity for. the fluo- .-rine in fluorine-bearing-water, possibly by the replacement oi a harmless radical by fluorine to iorm"the--insolubie; fluorapatite. Examples of "such "substances are the natural phosphate rocks which generaliyoccunin the form oi fluorapatite having'the g'eneraliormula 3Caa(l?0e) aCalz, as well as artificially prepared apatites, such-as hydroxy-apatitaor'other similar calcium phosphate compounds. 'All of thesecompounds seem to-have a marked amnityfor the fluorinein fluorinewear- 'ing waters-and act in an exchange reac-,

as human Eystem which method is tion whereby fluorine is exchanged for a relatively harmless radical or element in .the

treatment material with the formation of insolubl'e flnorapatite. Treatment material which commonly contain fluorine, such as the natural rock phosphate, and even the preferred bone, will generally require an initial processing to remove the fluorine present so as to render them most eflective mimesubsequent. removal of fluorine from the water. Such processing iorms'a'n imDOII- tant part or. the present invention and will be dealt within detail presently.

As previously indicated, the preferred iorm'oi' this invention makes use'oi' the afllnity of bone for: I

the removal 01' fluorine from water and, consequently, the following description uses this form as a specific exempliflcation oi the invention. It

is to be understood, however, that other similar calcium phosphate compounds maybe utilized instead of the preferred bone and the invention nu; be-limitedxonly m accordancewith the scope of theappended claims.

period of time, aiter'which the bone with its combined fluorine may be' removed from the water by sedimentation, vfiltration, or a combination of the two. I! desired, the water may be passed through afllter bed "consisting of the ground bone.

However, the .eiiectiveness of the bone may be greatlyv enhanced by a Dre-treatment operation, constituting an important part or the present invention, and its absorbing power can also be re newed after exhaustion bya simple treatment.

similar to the initial processing. In describing this treatment, results of actual laboratory and held tests will be utilized-in order to illustrate the invention in the most complete manner.

It has been repeatedly shown that animal bones contain fluorine. and that the amount varies with the intake oi-fluorine. Fossil bones, especially, have long been noted as high in fluorine content. the fluorine content increasing with the age of the bone, probably due to a prolongedcontact with water or soil containing calcium fluoride. Be the pre-treatment of this invention to remove the fluorine content will render .the bone most active for subsequent removal of fluorine from. water. Likewisathe same treatment may heapplied to natural or other calcium-phosphates containing fluorine, to render the same more eflective for the subsequent absorption of fluorine from water.

In the pre-treatment method of this invention, bone is' obtained freed from fat and most of the protein material by boiling in water. It is then crushed andboiled'in a dilute solution (approximately 2N) of sodium, hydroxideuntil it has lost acid. Subsequently the materialis washed, driedand'graded in'flneness.

Tap water, with sodium fluoride added to raise the fluorine concentration to 5 P. P. M., was

The ground bone may beadded to the desired quan tity of water and agitated therewith for a suitable shaken with bone prepared as Just described an 'end-over-end shaking machine. samples were shaken for two hours with variable amounts of bone of to all mesh. Fluorine analysis was subsequently made upon aliquot parts 01 =the filtrate by two difierent methods which gave results in, close agreement. Representative .flndingsoi these tests the following table Original concentration oi fluorine in water used, P. M.

hmounto lbonsused 15 mm N f 1.0 2.0 5.0 0.0 8.0 10.0

Fluorine concentration alter 0 hours treatment, P. P. M.

amen

From the'abovetabie it will be seen that the,

bone treatment was eii'ective in reducing the concentration of fluorine; the extent of its removal varying with theamount of bone used and the original fluoride concentration of the water. In these experiments, two grams of bone were from 6.1. P. M, whichv is a high concentration for drinking water supply and will produce the mel is endemic, gram of bone was effective; '40 in satisfactory removal of fluorine from the'sam amount of water.

Another group of tests demonstrated thereiation of fineness of grinding oi the bone to its eitectiv'eness in fluorine removal under the same conv ditions. In these tests, bone prepared as pre j viously described, but varying in fineness from, 10 to 100 mesh. was used in the treatment oi 1 water with an original fluorine content of 5 .P. P. M. under conditions substantiall the same I as those just described. Under the experimental conditions, bone of 10 to mesh. was not as eiiective as that which had been. given a flner grind. 0n the other hand hone oi as to fill mesh reduced-the fluorine concentration from 5 to .4 P. .P. M. The more finely ground material'was is the removal or. fluorine under the conditions described. Mom the standpoint of use in filters, however, bone'flner than 3.0 to mesh is apt recommended because of slowness of penetration The time of contact between bone and-the flu rine-bearing wateris'also a factor directingthe extent of removal." when water containing dine-v.1 line was allowed to, stand in contact with the. specially prepared bone for a relatively long pe riod of time before'it was fllteredofl, the removal 0! fluorine by a given amount oi'bone was more complete than that resulting from shaking the bone with the water for a two hour period. For; example. standing for ninety-six hours in contact with one grain ofprepared bone reduced the are presented in suflicient to reduce .the fluorine in 500 cc. of water which a .9 P. r. M. When the initial fluorine V somewhat more effective in the claimant oi fluorine removed. It is evident, therefore. that eflectiveness or the bone is demnnent to a cerg-v tain. extent upon its fineness or grind. Tire greater-the surface of contact the more completeconcentration of fluorine from 2 P. P. M. to 0, as compared with a concentration of .5 P. P. M. remaining in a sample of water shaken for a two hour period. It is noted, however, that the contact of two hours was amply sufilcient for reducing the fluorine concentration to below the toxic level.

Further tests were made to demonstrate the practicability of renewing or regeneratin bone which had been used to remove fluorine from water so as to renew its absorptive capacit for fluorine and thus render the material capable of indefinite re-use. It was demonstrated that the absorbed fluorine could be practically completely removed from the used bone by treating the bone with a dilute solution of sodium hydroxide, either with or without boiling, and then washing outthe excess hydroxide with water and neutralizing the last traces with an acid, such as hydrochloric, as in the initial processing. In this regeneration treatment, boiling inthe caustic solution' is not necessary if the time of contact is willciently long. Best activation of the bone is obtained by letting the bone stand over night in 0.2 to 0.5 normal sodium hydroxide. Agitation of the suspension would speed up the process and can be used if desired. The hydroxide is then washed out and the last traces neutralized with 0.1 normal acid for ten to fifteen minutes. Bone which had been twice renewed in this fashion was found to be equally as effective as the original material.

The chemistry of the removal of fluorine and fluorides from water by bone and other calcium phosphates has not been definitely proven, but it is believed to be in the nature of an exchange reaction. The unprepared bone is probably a carbonate fluorapatite and, while it has a certain afiinity for the fluorine in water, the presence of small amounts of fluorine in the bone will naturally detract from its absorptive capacity. Since fluorine combines readily with sodium, the pretreatment in a weak sodium hydroxide solution will remove the fluorine in the form of the soluble sodium fluoride, which is washed out with water, and leave a substantially pure carbonate apatite. When this material is contacted with fluorinebearing water, either by agitation with the water or by filtering the water through a bed of the material, it is believed that the fluorine displaces the CO3 radical to form the insoluble fluorapatite having the general formula (CaF)Ca4(PO4)a, the CO3 forming the relatively harmless carbonates of the alkaline earth metals with which th fluorine was associated in the water.

In regenerating the bone, the exhausted material, which has become essentially the fluorapatite, is treated as in the first instance with a dilute caustic solution followed by washing and neutralization which removes the fluorine in the form of the soluble sodium fluoride, and there.- generated material probably becomes an hydroxy-apatite and, as such, is again ready for the removal of fluorine from water. In subsequent uses. of the bone, after assuming the hydroxy form, the exchange reaction is probably effected aflinity can be enhanced by the pre-treatment described, and that the treatment materials can be regenerated and renewed indefinitely in the.

manner described.

Similarly, natural rock phosphate, whichis generally a fluorapatite, may be treated initially by caustic soda and acid neutralization to remove the fluorin and thus form an hydroxy-apatite for the treatment of fluorine contaminated water,

and this material may be regenerated from time i In the use of bone, specially pre-treated as previously described, a further processing step will materially improve the afiinity of the bone for fluorine. It has been found that calcining the prepared bone improves its water wetability and prevents troublesome putrefaction of the bone. It has been found that putrefaction may set in after about a month or six weeks use in treatment of water. This seems to be due to organisms of putrefaction in the water. By calcining the bone for about ten minutes at a'temperature of approximately 600 C. the tendency to putrify is entirely overcome. The protein content of the bone is not materially reduced by this treatment but is apparently changed to a form not susceptible to the organisms causing putrefaction. One

calcination is sufficient and need not be resorted to in subsequent regeneration treatments.

While the preferred media for the initial processing and the regeneration of the bone are dilute sodium hydroxide and a suitable acid, it is obviously within the scope of the invention to employ other materials of a similar nature for effecting the desired reaction, whichis the removal of fluorine from the material. For instance, the

40 bone might be treated in the first instance and in the regeneration treatments with a. solution of sodium chloride or of calcium chloride. In

such treatment the acid neutralization might not be necessary but could be employed to assure a neutral product. Furthermore. in the treatmentwhere sodium hydroxide is utilized'for initial preparation or re eneration, it will be obvious that any other suitable acidic substance may be used to remove the last traces of hydroxide. Whilc hydrochloric acid has been mentioned specifically, the same effect may be obtained by other acids, such as phosphoric or acetic acid. In fact. the latter has been used with marked success and has the advantage of being cheap and is not dangerous to use. Furthermore, the slurry or suspension could be neutralized by gassing with CO2. In other words. the caustic soda treatment is the most efiicient for initial or subsequent removal of fluorine from the treatment material but should be washed out thoroughl and thelast traces neutralized with any suitable acidic substance. Thus, since the function ofthe acid 1 treatment is to neutralize any traces of alkali it is obvious that any acid will affect the neutralization reaction. Manifestly, however, the use of acids which would substantially impair the fluorine removing ability of the treatment mate ial or that would leave dangerous or toxic reaction products is not recommended. 1

As a result of the treatment of water by t e material and process of' this invention, no de-- te t ble change in the taste of the water is noted. Provided the acid and alkali used in. the

prepa "ation f the material is completely removed, the pH of the treated water is not substantially difierent from the original. There may be some slight solution of the bone, which would be evidenced by a very slight increase in the phosphate ion concentration in the treated water. This increase might be considered desirable and is in no way detrimental.

Having described the treatment materials of the present invention which have been found effective in the removal of fluorine from drinking water supplies, and methods of treating such materials for beneficiation and regeneration thereof, together with Indicating in a general way manners in which these materials may be used in the treatment of drinking water supplies, we will now describe and illustrate a specific application of the invention as embodied in a particular apparatus, comprising a part of the invention, which is highly efiicient in the treatment of drinking water supplies. For this purpose the accompanying drawing will illustrate this convenient application of the method and in this drawing- Fig. 1 is an elevation of a water cooler embodying features of the invention and equipped with means for satisfactory removal of fluorine so as to provide a drinking water having a fluorine content not above the toxic level.

Fig. 2 is an enlarged perspective view of the filtering element of the water cooler.

In the drawing, the numeral 3 designates a base or foundation provided with a lower platform 4 for supporting a waste jar 5. By an appropriate bracket 6 the base also supports a drain member I communicating with the waste jar by means of the pipe section 8. It is understood that the drainage member I has a perforated false bottom or is provided with a center hole communicating with the pipe 8 for permitting excess water to drain into thewaste jar 5, in well-known manner. At its top the stand 3 supports a fiat base 9 which in turn supports a cooling reservoir or olla II! which is provided with a tap I I.

Inside of the olla I0, and comprising a feature of the present invention, is a filter element H. As shown in Fig. 2 this filter element comprises a main cylindrical body portion '62 which is preferably formed of porcelain. This body portion is open at its upper end, as at l3, but is closed at its lower end by means of a collar Hi which holds or secures a section of muslin or other appropriate porous medium over the lower end of the filter element.

The water supply is contained within the jar or bottle [5, generally the well-known five gallon bottle, which is inverted into the olla iii and supported at its upper end by the reduced .portion IS. The height of the filter element H is such that the neck of the bottle [5 extends a slight distance into the upper end l3 of the filter element. For the purpose of effectively removing fiuorine from a fluorine contaminated water in the contents of the bottle l5, the hollow interior of the filter element H is filled with a treatment material of the present invention, this material preferably taking the form of the preferred crushed bone initially pretreated as hereinbefore described. Water flows from the bottle I 5 through the bone filling in the filter element by gravity and is defluorinated by so doing. When the water level in the olla reaches the height of the lower end of the bottle neck the pressure is equalized and stops the flow of water until some is withdrawn from the olla. The olla I0 is porous and permits some water to seep through the walls. Upon evaporating it cools the stored water within the olla. Since all of the water contained within the bottle i5 must pass through the filter bed provided within the filter element II, it is assured ample contact with the active defiuorinating agent within the filter element and a properly defluorinated water is delivered from the faucet H. Knowing that each bottle contains five gallons of water, or whatever is its capacity, it is relatively simple to keep count of the bottles to determine the total amount of water filtered. Therefore, knowing the effect of the material within the filter element I I, it is a relatively simple matter to calculate when this material is exhausted and ineffective in reducing the fiuorine content below the toxic level. Upon this condition being reached, the filtering material may be removed and regenerated in accordance with the principles of this invention or a replacement filter element ,Il equipped with active defluorinating filtering material may be substituted for the exhausted element.

Thus, where it is impractical to treat entire municipal water supplies or the entire contents of wells, the invention may readily be embodied in a device of the foregoing type and used to supply defluorinated drinking water in homes, schools, ofilces and the like.

It is also possible to employ the treatment materials of the present invention in pressure type filters simliar to the conventional zeolite water softeners. In other words the material may be used in the conventional water softener in place of the zeolite normally used therein. However, this pressure type filter should be used in connection with a meter in order to determine the amount of water passed through and hence the time at which the filter medium becomes exhausted. Such a pressure filter may be equipped with a meter to be read manually to determine when the filter medium is exhausted but preferably should be provided with an automatic alarm which will indicate precisely when such an amount of water has passed through that the filter medium would be exhausted and incapable of reducing the fluorine content below the toxic level.

Thus the practicability of the use of the bone treatment of the present invention for fluorine removal from water in a faucet filter or cooler filter for home, ofiice and school use, is readily apparent. It is also feasible for use on a large scale for treatment of municipal water supplies. In view of the fact that the fluorine absorbing power of the bone can be repeatedly renewed, it is believed apparent that the treatment described herein is economical and eminently satisiactory in the treatment of entire municipal water supplies.

The present invention employs, among its novel features, a method of initially preparing bone and other apatites and phosphatic compounds for use in the removal of fluorine, the treatment of fiuorine bearing water or other liquids with such specially prepared materials and a method of treating spentmaterial for renewing its fiuorine absorbing powers.

While the invention has been herein described as applied to the treatment of drinking water supplies, it is apparent that it is equally applicable to the purification of other liquids designed for human consumption. For instance,- in the Pacific northwest, apples are sprayed with a fluorine spray. Culls containing fluorine cannot assasco profltably be washed so are pressed for cider without cleaning. Obviously the method described herein can be successfully applied to such fluorine containing cider and will be eflective in reducing the fluorine content to a point below the toxic level. Therefore, wherever in the speciflcation and claims the term water" is used, such term is obviously meant to include any potable liquid ultimately designed for human consumptlon.

Thus this invention comprises broadly the use of bone and other calcium phosphates for removal of fluorine from water and other potable liquids. It has been shown, as an important feature hereof, that treatment of the bone with an alkali followed by a short acid treatment will materially enhance its fluorine absorbing power, and a similar treatment after exhaustion will reactivate the bone and renew its fluorine absorbing power.

In the initial preparation of the bone calcination has been found desirable because it inhibits .any tendency of the bone to putrefy and increases its wetability. "In addition, the calcination step makes the bone harder and less sub- ,lect to lossesby attrition and dissolution; the surface area is increased, by the resulting porosity, thus increasing the contact area which results in enhanced capacity for fluorine removal; and more fluorine is removed from the bone which also serves to increase its fluorine removing power. It has been determined that initial processing of-the bone by treatment with alkali, washing, neutralizing with acid, calcining for about ten minutes at temperatures from about 400 to 600 C.,followed by a short treatment with acid, yields an excellent bone product which is highly efllcient in the removal of fluorine from fluorine contaminated liquids.

The pH of'the water, the temperature of the reacting mixture, and the presence of other salts in the water seem to have no effect on the fluorine removal process.

While herein there have been discussedseveral substances containing calcium phosphate or tricalcium phosphate which might be useful in the removal of fluorine from water, the preferred bone, treated as herein described, is more than twice as effective and emcient in the treatment of water for fluorine removal as any other substance now known to us.

What is claimed is:

1. The process of removing fluorine from fluorine contaminated water which comprises, treating crushed bone with a solution of an alkali to remove fluorine therefrom, washing out the alkali and fluorine removed thereby, neutralizing the bone with an acid, and intimately contacting the water to be treated with the thus defluorinated bone.

2. The process of removing fluorine from fluorine contaminated water which comprises, treating crushed bone with a soution of sodium hydroxide to remove fluorlne'therefrom, washing out the sodium hydroxide and fluorine removed thereby, neutralizing the bone with an acid, and intimately contacting the water to be treated with the thus defluorinated bone.

.3. The process of removing fluorine from fluorine contaminated water which comprises,

treating crushed bone with a solution of sodium hydroxide to remove fluorine therefrom, washing out the sodium hydroxide and fluorine removed thereby, neutralizing the bone with an acid, calcining the bone, and intimately contacting the water to be treated with the thus treated bone.

4. The process of removing fluorine from fluorine contaminated water which comprises, treating crushed bone with a solution of sodium hydroxide to remove fluorine therefrom, wash-,

ing out the sodium hydroxide and fluorine removed thereby, neutralizing the bone with an acid, calcining the bone, treating the calcined bone with an acid, and intimately contacting the water to be treated with the thus treated bone.

5. The process of activating bone for use as an agent for the removal of fluorine from fluorine contaminated water which comprises, treating the crushed bone-with a solution of an alkali, washing out the alkali, and neutralizing the thus treated bone with an acid.

6. The process of activating bone for use as an agent for the removal of fluorine from fluorine contaminated water which comprises, treating the crushed bone with a solution of an alkali, washing out the alkali, neutralizing the bone with an acid, and calcining the thus treated bone.

7. The process of activating bone for use as an agent for the removal of fluorine from fluorine contaminated water which comprises, treating the crushed bone with a solution of sodium hydroxide, washing out the sodium hydroxide, and neutralizing the thus treated bone with an acid.

8. The process of activating bone for use as an agent for the removal of fluorine from fluorine contaminated water which comprises, treating the crushed bone with a solution of sodium hydroxide, washing out the sodium hydroxide, and neutralizing the thus treated bone with hydrochloric acid.

9. The process of activating bone for use as an agent for the removal of fluorine from fluorine contaminated water which comprises, treating the crushed bone with a solution of sodium hydroxide, washing out the sodium hydroxide, and neutralizing the thustreated bone with acetic acid.

10. The process of activating bone for use as an agent for the removal of fluorine from fluorine contaminated water which comprises, treating the crushed bone with a solution of sodium hydroxide, washing out the sodium hydroxide, and neutralizing the thus treated bone with carbon dioxide.

11. As a new product, an agent for the removal of fluorine from fluorine contaminated water comprising, ground bone substantially freed of fluorine by treatment with a solution of an alkali and subsequent neutralization with an acid.

12. As a new product, an agent for the removal of fluorine from fluorine contaminated water comprising, ground bone which has been treated with a solution of sodium hydroxide, washed, neutralized, and calcined.

HOWARD V. BlldITI-I. MARGARET 0. SMITH. 

